A pressure swing adsorption gas separation system and separation method

Abstract

The present invention discloses a pressure swing adsorption gas separation system and a separation method. The separation system includes an adsorption tower, a reverse discharge pipeline, a flushing out pipeline, a flushing in pipeline, a forward discharge pipeline, a pressure equalizing pipeline, a first pressure equalizing and final pressure boosting pipeline, a product gas transmission pipeline, a final filling regulating valve, a high-pressure raw gas pipeline and a low-pressure raw gas pipeline. The separation method is that the adsorption step in the separation process includes two adsorption steps, a high-pressure main adsorption step and a low-pressure auxiliary adsorption step, and the high-pressure raw gas corresponds to the high-pressure main adsorption step when entering the adsorption tower, and corresponds to the low-pressure auxiliary adsorption step when entering the adsorption tower. The present invention innovatively optimizes the pressure swing adsorption process starting from the adsorption step to improve the recovery rate, and the recovery rate improvement effect is significant, while saving the compression energy consumption of the low-pressure raw gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas separation, and in particular relates to a pressure swing adsorption gas separation system and a separation method. Background Art

[0002] Pressure swing adsorption technology is an efficient gas separation technology that utilizes the differences in adsorption capacity of adsorbents for different gases, as well as the characteristics that the adsorption amount increases with increasing pressure and decreases with decreasing pressure, to achieve separation and purification of different gases through pressure changes.

[0003] Pressure swing adsorption technology can be used to separate and purify weakly adsorbed gases such as hydrogen, helium, oxygen, nitrogen, etc., and can also be used to purify strongly adsorbed gases such as methane, ethane, carbon monoxide, carbon dioxide, etc. It is mainly used in energy, chemical, oil refining, metallurgy, medicine and other industries, and can be used for the purification and comprehensive utilization of various industrial exhaust gases.

[0004] Reducing the investment and energy consumption of pressure swing adsorption devices and improving the recovery rate of pressure swing adsorption devices are important goals for pressure swing adsorption technology developers.

[0005] In terms of improving the recovery rate of pressure swing adsorption devices, in addition to the research and development of new high-efficiency adsorbents, the development of new process flows is the most important research direction. Among them, how to improve the regeneration effect is the most studied. For the flushing process, giving full play to the efficiency of the downstream gas is the main means to improve the yield. For example, patent CN1298410C uses two downstream gas buffer tanks to achieve staggered flushing of downstream gas, patent 100588449C uses four regulating valves to achieve three staggered flushing of downstream gas, and patent CN112919414A proposes a pressure swing adsorption hydrogen purification method with low-pressure flushing regeneration, which further improves the flushing regeneration effect; for the vacuum regeneration process, adding some flushing gas during the vacuum process can also improve the regeneration effect, such as patent CN210751946U. In addition, by increasing the number of pressure equalization times and changing the pressure equalization method, the separation efficiency can also be improved. In addition to the conventional upper and lower pressure equalization, patent CN 113041782 B also proposes a composite pressure equalization method.

[0006] The above methods cannot reduce energy consumption and may even increase pressure swing adsorption energy consumption. Therefore, designing a pressure swing adsorption gas separation system and separation method that can improve efficiency and reduce energy consumption has become a technical problem that needs to be urgently solved by technicians in the relevant technical field. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a pressure swing adsorption gas separation system and separation method, which optimizes the pressure swing adsorption process from the adsorption step to improve the recovery rate while reducing compression energy consumption.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A pressure swing adsorption gas separation system comprises several adsorption towers, a reverse discharge gas pipeline and a flushing outlet pipeline connected to the adsorption tower, and a flushing inlet pipeline, a forward discharge pipeline, a pressure equalizing pipeline, a first pressure equalizing and final pressure boosting pipeline and a product gas transmission pipeline connected from the adsorption tower; the first pressure equalizing and final pressure boosting pipeline and the product gas transmission pipeline are connected through a final filling regulating valve, and the adsorption towers are respectively connected to a high-pressure raw gas pipeline for providing high-pressure raw gas and a low-pressure raw gas pipeline for providing low-pressure raw gas.

[0010] Furthermore, a low-pressure raw gas flow control regulating valve is provided on the low-pressure raw gas pipeline.

[0011] A separation method for a pressure swing adsorption gas separation system, wherein the adsorption steps in the separation process include two adsorption steps: a high-pressure main adsorption step and a low-pressure auxiliary adsorption step. Moreover, when the high-pressure raw gas enters the adsorption tower, it corresponds to the high-pressure main adsorption step, and when the low-pressure raw gas enters the adsorption tower, it corresponds to the low-pressure auxiliary adsorption step.

[0012] Furthermore, each adsorption tower undergoes the following steps in a cyclic sequence:

[0013] High-pressure main adsorption step: high-pressure feed gas enters the adsorption tower from the inlet end, strong adsorbates are adsorbed, and weak adsorbates flow out of the adsorption tower;

[0014] Multiple pressure reduction steps: the gas in the adsorption tower flows out of the adsorption tower from one or both of the outlet and inlet ends of the adsorption tower, and the pressure in the adsorption tower is reduced;

[0015] Regeneration step: The strong adsorbate in the adsorption tower is desorbed from the adsorbent and leaves the adsorption tower, and the adsorbent is regenerated;

[0016] Multiple pressurization steps: using gas from other adsorption towers to pressurize the adsorption tower;

[0017] Low-pressure auxiliary adsorption step: low-pressure feed gas enters the adsorption tower from the inlet end, strong adsorbents are adsorbed, and weak adsorbents increase the pressure in the adsorption tower;

[0018] Final pressure-raising step: The step in which the pressure in the adsorption tower is raised to the pressure of the high-pressure main adsorption step.

[0019] Preferably, the depressurization step provides pressurized gas to the adsorption tower in the pressurization step or provides flushing gas to the adsorption tower in the flushing regeneration step or directly discharges the adsorption tower as waste gas.

[0020] Preferably, in the regeneration step, the regeneration method is one of flushing regeneration and vacuum regeneration, or a combination of the two methods.

[0021] Preferably, the low-pressure auxiliary adsorption step and the pressure-raising step are performed simultaneously or separately.

[0022] Preferably, in the pressurizing step, the gas from other adsorption towers enters the adsorption tower from one or both of the outlet and inlet ends of the adsorption tower.

[0023] Preferably, the low-pressure feed gas is one or more streams, and correspondingly, the low-pressure auxiliary adsorption step is one or more.

[0024] Preferably, the pressurized gas in the final pressurization step comes from one or two combined gases of the weakly adsorbed material at the outlet of the adsorption tower in the high-pressure main adsorption step and the high-pressure feed gas.

[0025] Preferably, the high-pressure feed gas and the low-pressure feed gas are the same gas, and the low-pressure feed gas is a gas obtained by reducing the pressure of a portion of the high-pressure feed gas.

[0026] Preferably, the high-pressure feed gas and the low-pressure feed gas are two gases with different pressures and compositions.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention is scientifically and rationally designed. It is the first to optimize the pressure swing adsorption process from the adsorption step to improve the recovery rate, and the recovery rate improvement effect is significant. At the same time, it can also save the energy consumption of raw gas compression. The present invention designs the adsorption step into a high-pressure main adsorption step and a low-pressure auxiliary adsorption step, introduces part of the raw gas into the adsorption tower for adsorption at high pressure, constituting the high-pressure main adsorption step, and introduces part of the raw gas into the adsorption tower for adsorption at low pressure, constituting the low-pressure auxiliary adsorption step. In this way, without increasing the volume of the adsorption tower and the number of adsorption towers, the total feed adsorption time of the adsorption tower is increased, the gas recovery rate and the processing capacity of the unit adsorbent are improved, and the overall performance of the system is improved. At the same time, since the low-pressure raw gas entering the adsorption tower in the low-pressure auxiliary adsorption step does not need to be compressed under high pressure, the compressor and compression energy consumption can be saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the principle of the present invention.

[0030] Figure 2 Effect of feed adsorption time on hydrogen recovery.

[0031] Figure 3 Effect of feed adsorption time on adsorbent processing capacity.

[0032] Figure 4 This is a process flow chart of an example of the present invention.

[0033] The names corresponding to the reference numerals are:

[0034] 1- High-pressure raw gas pipeline, 2- Low-pressure raw gas pipeline, 3- Reverse discharge pipeline, 4- Flushing outlet pipeline, 5- Fourth equalizing pressure / fifth equalizing pressure pipeline, 6- Flushing inlet pipeline, 7- Forward discharge pipeline, 8- Second equalizing pressure / third equalizing pressure pipeline, 9- First equalizing pressure and final boosting pipeline, 10- Product gas export pipeline, 11~110- Program-controlled valve, T- Adsorption tower, HV101- Final filling regulating valve, HV201- Low-pressure raw gas flow control regulating valve. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] like Figure 1 and Figure 4 As shown, the present invention provides a pressure swing adsorption gas separation system comprising several adsorption towers T, a reverse bleed gas pipeline 3 and a flush outlet pipeline 4 connected to the adsorption towers T, as well as a flush inlet pipeline 6, a downstream bleed gas pipeline 7, a pressure equalizing pipeline, a first pressure equalizing and final pressure boosting pipeline 9, and a product gas export pipeline 10 extending from the adsorption towers. The first pressure equalizing and final pressure boosting pipeline 9 and the product gas export pipeline 10 are connected via a final filling regulating valve HV101. The adsorption towers T are connected to a high-pressure feed gas pipeline 1 for providing high-pressure feed gas and a low-pressure feed gas pipeline 2 for providing low-pressure feed gas. The low-pressure feed gas pipeline 2 is equipped with a low-pressure feed gas flow control regulating valve HV201. The downstream bleed gas pipeline 7 and the flush inlet pipeline 6 are connected via a downstream bleed regulating valve PV101, and the first pressure equalizing and final pressure boosting pipeline 9 and the product gas export pipeline 10 are connected via a final filling regulating valve HV101. The pressure equalizing pipeline includes a second pressure equalizing / third pressure equalizing pipeline 8 and a fourth pressure equalizing / fifth pressure equalizing pipeline 5 .

[0037] The present invention is scientifically and rationally designed. It is the first to optimize the pressure swing adsorption process from the adsorption step to improve the recovery rate, and the recovery rate improvement effect is significant. At the same time, it can also save the energy consumption of low-pressure raw gas compression. The present invention designs the adsorption step into a high-pressure main adsorption step and a low-pressure auxiliary adsorption step, introduces part of the raw gas into the adsorption tower for adsorption under high pressure, constituting the high-pressure main adsorption step, and introduces part of the raw gas into the adsorption tower for adsorption under low pressure, constituting the low-pressure auxiliary adsorption step. In this way, without increasing the volume of the adsorption tower and the number of adsorption towers, the total feed adsorption time of the adsorption tower is increased, the gas recovery rate and the processing capacity of the unit adsorbent are improved, and the overall performance of the system is improved. At the same time, since the low-pressure raw gas entering the adsorption tower in the low-pressure auxiliary adsorption step does not need to be compressed under high pressure, the compressor and compression energy consumption can be saved.

[0038] like Figure 1 and Figure 4 As shown, the present invention provides a pressure swing adsorption gas separation method. The adsorption step during the separation process includes two adsorption steps: a high-pressure main adsorption step and a low-pressure auxiliary adsorption step. In addition, when the high-pressure feed gas enters the adsorption tower, it corresponds to the high-pressure main adsorption step, and when the low-pressure feed gas enters the adsorption tower, it corresponds to the low-pressure auxiliary adsorption step. Each adsorption tower undergoes the following steps in a cyclic sequence:

[0039] High-pressure main adsorption step: High-pressure raw gas enters the adsorption tower from the inlet end of the adsorption tower, the strong adsorbent is adsorbed, and the weak adsorbent flows out of the adsorption tower.

[0040] Multiple depressurization steps: Gas in the adsorption tower flows out of the adsorption tower from one or both of its outlet and inlet ends, reducing the pressure inside the adsorption tower. The depressurization step provides pressurized gas to the adsorption tower in the pressurization step, provides flushing gas to the adsorption tower in the flushing and regeneration step, or directly discharges the adsorption tower as waste gas.

[0041] Regeneration step: The strongly adsorbed substance in the adsorption tower is desorbed from the adsorbent and leaves the adsorption tower, and the adsorbent is regenerated. The regeneration method in the regeneration step is one of flushing regeneration and vacuum regeneration, or a combination of the two methods.

[0042] Multiple pressurization steps: The gas from other adsorption towers is used to pressurize the adsorption tower. During the pressurization step, the gas from other adsorption towers enters the adsorption tower from one or both of the outlet and inlet ends of the adsorption tower.

[0043] Low-pressure auxiliary adsorption step: Low-pressure feed gas enters the adsorption tower from its inlet. Strong adsorbates are adsorbed, while weak adsorbates increase the pressure within the tower. This step can be performed simultaneously with or separately from the pressure-raising step. The low-pressure feed gas may be one or more streams, and accordingly, there may be one or more low-pressure auxiliary adsorption steps.

[0044] Final pressure-raising step: The step in which the pressure in the adsorption tower is raised to the pressure of the high-pressure main adsorption step. The pressurized gas in the final pressure-raising step comes from one or both of the weakly adsorbed material at the outlet of the adsorption tower and the high-pressure feed gas.

[0045] The high-pressure feed gas and the low-pressure feed gas are the same gas, and the low-pressure feed gas is a portion of the high-pressure feed gas reduced in pressure. Alternatively, the high-pressure feed gas and the low-pressure feed gas are two gases with different pressures and compositions.

[0046] The present invention is scientifically and rationally designed. It is the first to optimize the pressure swing adsorption process from the adsorption step to improve the recovery rate, and the recovery rate improvement effect is significant. At the same time, it can also save the energy consumption of low-pressure raw gas compression. The present invention designs the adsorption step into a high-pressure main adsorption step and a low-pressure auxiliary adsorption step, introduces part of the raw gas into the adsorption tower for adsorption under high pressure, constituting the high-pressure main adsorption step, and introduces part of the raw gas into the adsorption tower for adsorption under low pressure, constituting the low-pressure auxiliary adsorption step. In this way, without increasing the volume of the adsorption tower and the number of adsorption towers, the total feed adsorption time of the adsorption tower is increased, the gas recovery rate and the processing capacity of the unit adsorbent are improved, and the overall performance of the system is improved. At the same time, since the low-pressure raw gas entering the adsorption tower in the low-pressure auxiliary adsorption step does not need to be compressed under high pressure, the compressor and compression energy consumption can be saved.

[0047] The present invention designs the adsorption step into a high-pressure main adsorption step and a low-pressure auxiliary adsorption step, dividing the raw gas into two streams: high-pressure raw gas and low-pressure raw gas. The high-pressure raw gas enters the adsorption tower for adsorption in the high-pressure main adsorption step, and a weakly adsorbed product is produced at the outlet of the adsorption tower, constituting the high-pressure main adsorption step. The low-pressure raw gas enters the adsorption tower for adsorption when the pressure is lower than the adsorption pressure, constituting the low-pressure auxiliary adsorption step. The low-pressure auxiliary adsorption step is performed simultaneously with the pressure-increasing step. In the low-pressure auxiliary adsorption step, the strong adsorbent in the raw gas is adsorbed, and the weak adsorbent is used to increase the pressure of the adsorption tower. By introducing two raw gas feeding steps, the low-pressure auxiliary adsorption step and the high-pressure main adsorption step, a portion of the raw gas that originally entered the adsorption tower in the high-pressure main adsorption step enters the adsorption tower for adsorption in the low-pressure auxiliary adsorption step, thereby increasing the feed adsorption time of the adsorption tower, reducing the feed amount and the empty tower linear velocity of the high-pressure main adsorption step, and improving the processing capacity per unit adsorbent and the gas recovery rate.

[0048] Each adsorption tower cycle of the present invention goes through the following steps in sequence:

[0049] High-pressure main adsorption step: High-pressure raw gas enters the adsorption tower from the inlet end of the adsorption tower, the strong adsorbent is adsorbed, and the weak adsorbent flows out of the adsorption tower.

[0050] Multiple pressure reduction steps: the gas in the adsorption tower flows out of the adsorption tower from one or both of the outlet and inlet ends of the adsorption tower, and the pressure of the adsorption tower is gradually reduced. The pressure reduction step provides boosting gas for the adsorption tower in the boosting step or provides flushing gas for the adsorption tower in the flushing regeneration step or directly discharges the adsorption tower as waste gas.

[0051] Regeneration step: The strong adsorbent in the adsorption tower is desorbed from the adsorbent and leaves the adsorption tower, and the adsorbent is regenerated. The regeneration method is one of flushing regeneration and vacuum regeneration or a combination of the two methods.

[0052] Multiple pressurization steps: Use gas from other adsorption towers to pressurize the adsorption tower. The pressure can be increased from one or a combination of the outlet and inlet ends of the adsorption tower.

[0053] Low-pressure auxiliary adsorption step: low-pressure raw gas enters the adsorption tower from the inlet end of the adsorption tower, the strong adsorbent is adsorbed, and the weak adsorbent increases the pressure in the adsorption tower. The low-pressure adsorption step and the pressure increase step are carried out simultaneously or separately; there are one or more low-pressure adsorption steps.

[0054] Final pressurization step: the step of increasing the pressure in the adsorption tower to the high-pressure adsorption pressure. The final pressurization gas comes from the combination of one or two streams of weak adsorbent at the outlet of the adsorption tower in the high-pressure main adsorption step and high-pressure feed gas.

[0055] The low-pressure raw gas and the high-pressure raw gas are the same raw gas; or, the low-pressure raw gas and the high-pressure raw gas are two raw gases with different pressures and compositions.

[0056] The low-pressure raw gas can be one or more streams.

[0057] In addition to the factors affecting the pressure swing adsorption separation effect, adsorption pressure, feed gas composition, adsorbent performance, pressure equalization times, and regeneration method, the feed adsorption time also has a significant impact on the separation effect. The numerical simulation method is used to simulate the pressure swing adsorption hydrogen extraction process. The results show that extending the adsorption time can significantly improve the hydrogen recovery rate and the processing capacity of the adsorbent. The effect of adsorption time on hydrogen recovery rate is as follows: Figure 2 As shown in Figure 2, the effect of adsorption time on treatment capacity is as follows: Figure 3 As shown. Conventional methods for increasing adsorption time are to increase the volume of the adsorption tower or increase the number of feed adsorption towers, which will significantly increase the investment in the adsorption device. The present invention provides a high-pressure main adsorption step and a low-pressure auxiliary adsorption step, introduces a portion of the feed gas into the adsorption tower for adsorption during the low-pressure auxiliary adsorption stage, and performs the low-pressure adsorption step and the pressure-boosting step simultaneously, thereby avoiding increasing the number of adsorption towers and the volume of the adsorption towers. By adding a low-pressure auxiliary adsorption step, the time of the adsorption tower feed adsorption step can be significantly increased, the recovery rate of the device can be improved, and the economic performance of the device can be improved.

[0058] The technology of the present invention is described in more detail below through specific examples.

[0059] like Figure 4 As shown, the present invention provides a pressure swing adsorption gas separation system and separation method, including 10 adsorption towers T, a high-pressure raw gas pipeline 1, a low-pressure raw gas pipeline 2, a product gas pipeline 10, a reverse discharge gas pipeline 3, a flushing outlet pipeline 4, a first equalizing and final pressure-boosting pipeline 9, a second equalizing / third equalizing pipeline 8, a fourth equalizing / fifth equalizing pipeline 5, a forward discharge pipeline 7, a flushing inlet pipeline 6, and programmable valves 11-110, a final charging regulating valve HV101, a forward discharge regulating valve PV101, and a low-pressure raw gas flow control regulating valve HV201. The 10 adsorption towers T are numbered T1-T10 in sequence.

[0060] This example uses a 10-1-5 / P process, with a process sequence as shown in Table 1. This process involves 10 adsorption towers, one adsorption tower, four pressure equalization steps, and flushing and regeneration. There are low-pressure and high-pressure adsorption steps. The high-pressure feed gas pressure is 3.0 MPaG, and the low-pressure feed gas pressure is 2.2 MPaG. The two feed gases have the same composition as shown in Table 2, and the temperature is 40°C. The cycle process, taking adsorption tower T1 as an example, is as follows:

[0061] Process 1 High-pressure adsorption step (A): Step 1, Step 2, the high-pressure feed gas flows into the adsorption tower T1 through the high-pressure feed gas pipeline 1 and the feed gas valve 11, the impurities are adsorbed by the adsorbent in the adsorption tower T1, and the hydrogen is sent out of the system through the product gas valve 101 and the product gas pipeline 10, i.e., the product gas.

[0062] Process 2 first equalizing and reducing pressure step (1D): Step 3, close valves 11 and 101, open valves 91 and 93, the adsorption tower T1 and the adsorption tower T3 are connected through the first equalizing and final pressure-boosting pipeline 9, and the adsorption tower T1 and the adsorption tower T3 perform the first equalizing pressure, that is, the adsorption tower T1 is the first equalizing and reducing pressure step, and the adsorption tower T3 is the first equalizing and increasing pressure step.

[0063] Process 3 second pressure equalization and pressure reduction step (2D): Step 4, close valve 91, open valves 81 and 84, the adsorption tower T1 and the adsorption tower T4 are connected through the second pressure equalization / third pressure equalization pipeline 8, the adsorption tower T1 and the adsorption tower T4 perform the second pressure equalization, that is, the adsorption tower T1 is the second pressure equalization and pressure reduction step, and the adsorption tower T4 is the low-pressure adsorption and second pressure equalization and pressure increase step.

[0064] Process 4: The third pressure equalization and pressure reduction step (3D): Step 5, close valve 84, open valve 85, the adsorption tower T1 and the adsorption tower T5 are connected through the second pressure equalization / third pressure equalization pipeline 8, and the adsorption tower T1 and the adsorption tower T5 perform the third pressure equalization, that is, the adsorption tower T1 is the third pressure equalization and pressure reduction step, and the adsorption tower T5 is the low-pressure adsorption third pressure equalization and pressure increase step.

[0065] Process 5: Fourth pressure equalization and pressure reduction step (4D): Step 6, close valves 84 and 85, open valves 51 and 56, the adsorption tower T1 and the adsorption tower T6 are connected through the fourth pressure equalization / fifth pressure equalization pipeline 5, and the adsorption tower T1 and the adsorption tower T6 perform the fourth pressure equalization, that is, the adsorption tower T1 is the fourth pressure equalization and pressure reduction step, and the adsorption tower T6 is the fourth pressure equalization and pressure increase step.

[0066] Process 6 fifth equalizing pressure reduction and sequential release step (5DP): Step 7, close valve 56, open valves 57, 71, 68, 69 and PV101, adsorption tower T1 and adsorption tower T7 are connected through the fourth equalizing pressure / fifth equalizing pressure pipeline 5, adsorption tower T01 and adsorption tower T07 perform the fifth equalizing pressure, that is, adsorption tower T1 is the fifth equalizing pressure reduction step, and adsorption tower T7 is the fifth equalizing pressure boosting step; at the same time, adsorption tower T1 and adsorption towers T08 and T09 are connected through sequential release pipeline 7, sequential release regulating valve PV101, and flushing pipeline 6, and adsorption tower T1 provides flushing regeneration gas for adsorption towers T8 and T9.

[0067] Process 7 sequential release step (PP): Step 8, close valves 51 and 57, continue to open valve 71 and PV101, and the sequential release step of adsorption tower T1 continues to provide flushing regeneration gas for adsorption towers T8 and T9.

[0068] Process 8 Reversal Step (D): Steps 9 and 10, close valve 71, open valve 31, and the gas in adsorption tower T1 flows out of the system through the reverse discharge pipeline 3 in the opposite direction of adsorption. In the reverse step, part of the strong adsorbent is desorbed.

[0069] Process 9 Flushing step (P): Steps 11-14, close valve 31, open valves 41 and 61, adsorption tower T1 receives the forward discharge gas from adsorption towers T3 and T4, backwashes the adsorption bed in the opposite direction of the airflow during adsorption, and the flushing waste gas flows out of the system through the flushing outlet pipe 4.

[0070] Process 10 fifth equalizing pressure boosting step (5R): Step 15, close valves 41 and 61, open valves 51 and 55, the adsorption tower T1 and the adsorption tower T5 are connected through the fourth equalizing pressure / fifth equalizing pressure pipeline 5, the adsorption tower T1 and the adsorption tower T5 perform the fifth equalizing pressure, that is, the adsorption tower T1 is the fifth equalizing pressure boosting step, the adsorption tower T5 is the fifth equalizing pressure reducing step, and T5 also provides flushing regeneration gas for other adsorption towers at the same time.

[0071] Process 11 fourth equalizing and boosting step (4R): Step 16, close valve 55, open valve 56, adsorption tower T1 and adsorption tower T6 are connected through the fourth equalizing / fifth equalizing / pipeline 5, and adsorption tower T1 and adsorption tower T5 perform the fourth equalizing, that is, adsorption tower T1 is the fourth equalizing and boosting step, and adsorption tower T6 is the fourth equalizing and reducing step.

[0072] Process 12 low-pressure adsorption and third equalizing pressure boosting step (3AR): Step 17, close valve 51, open valves 21, 81 and 87, and the low-pressure raw gas enters the adsorption tower T1 through the regulating valve HV201 and the low-pressure raw gas pipeline 2. At the same time, the adsorption tower T1 and the adsorption tower T7 are connected through the second equalizing pressure / third equalizing pressure pipeline 8, and the adsorption tower T1 and the adsorption tower T7 perform the third equalizing pressure, that is, the adsorption tower T1 is the low-pressure adsorption and third equalizing pressure boosting step, and the adsorption tower T7 is the third equalizing pressure reducing step.

[0073] Process 13 low-pressure adsorption and second equalizing pressure boosting step (2AR): Step 18, close valve 87, open valve 88, the low-pressure raw gas continues to enter the adsorption tower T1 through the regulating valve HV201 and the low-pressure raw gas pipeline 2. At the same time, the adsorption tower T1 and the adsorption tower T8 are connected through the second equalizing pressure / third equalizing pressure pipeline 8, and the adsorption tower T1 and the adsorption tower T8 perform the second equalizing pressure, that is, the adsorption tower T1 is the low-pressure adsorption and second equalizing pressure boosting step, and the adsorption tower T8 is the second equalizing pressure reducing step.

[0074] Process 14: First pressure equalization and boosting step (1R): Step 19, close valves 21, 81, and 88, open valves 91 and 99, and connect the adsorption tower T1 and the adsorption tower T9 through the first pressure equalization and final boosting pipeline 9. The adsorption tower T1 and the adsorption tower T9 perform the first pressure equalization, that is, the adsorption tower T1 is the first pressure equalization and boosting step, and the adsorption tower T9 is the first pressure equalization and depressurization step.

[0075] Process 15: Final pressure boosting step (FR): Step 20: Close valve 99, open regulating valve HV101, connect adsorption tower T1 to product gas pipeline 10 through first pressure equalization and final pressure boosting pipeline 9 and regulating valve HV101, and use product hydrogen to finally boost the pressure of adsorption tower T1 to the adsorption pressure.

[0076] Table 1 10-1-5 / P process timing chart

[0077]

[0078] Note: A: high-pressure adsorption step, 1D: first equalizing and depressurizing step, 2D: second equalizing and depressurizing step, 3D: third equalizing and depressurizing step, 4D: fourth equalizing and depressurizing step, 5DP: fifth equalizing and depressurizing and forward release step, PP: forward release step, D: reverse release step, P: flushing step, 5R: fifth equalizing and pressure-increasing step, 4R: fourth equalizing and pressure-increasing step, 3AR: low-pressure adsorption and third equalizing and pressure-increasing step, 2AR: low-pressure adsorption and second equalizing and pressure-increasing step, 1R: first equalizing and pressure-increasing step, FR: final pressure-increasing step.

[0079] Table 2 Composition of raw gas

[0080] composition <![CDATA[H2]]> <![CDATA[N2]]> CO <![CDATA[CH4]]> <![CDATA[CO2]]> Content / mol% 78.8 10.6 2.6 1.9 6.1

[0081] The process of the present invention is used to produce product gas with a hydrogen purity of 99.9% and a CO content of less than 10 ppm. The flow rate of the low-pressure raw gas is 30% of the flow rate of the high-pressure raw gas, and the hydrogen recovery rate is 90.4%. The conventional pressure swing adsorption process in which the raw gas enters the adsorption tower in the high-pressure adsorption step without introducing the low-pressure adsorption step is 89.7%, that is, the hydrogen recovery rate is increased by 0.7 percentage points. The flow rate of the raw gas is 15000 Nm 3 / h pressure swing adsorption device can increase hydrogen production by 695,000 Nm3 per year 3 , the entire life cycle (20 years) can produce an additional 13.9 million Nm3 of hydrogen 3 .

[0082] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are intended to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or refinements made to the main design concept and spirit of the present invention that have no substantive significance, provided that the technical problems they solve are still consistent with those of the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields should also be included in the patent protection scope of the present invention.

Claims

1. A pressure swing adsorption gas separation system, comprising a plurality of adsorption towers (T), a reverse discharge pipeline (3) and a flushing outlet pipeline (4) connected to the adsorption tower (T), and a flushing inlet pipeline (6), a forward discharge pipeline (7), a pressure equalizing pipeline, a first pressure equalizing and final pressure boosting pipeline (9) and a product gas transmission pipeline (10) connected from the adsorption tower (T); the first pressure equalizing and final pressure boosting pipeline (9) and the product gas transmission pipeline (10) are connected via a final filling regulating valve (HV101), characterized in that: The adsorption tower (T) is respectively connected to a high-pressure raw gas pipeline (1) for providing high-pressure raw gas and a low-pressure raw gas pipeline (2) for providing low-pressure raw gas.

2. A pressure swing adsorption gas separation system according to claim 1, characterized in that: A low-pressure raw gas flow control regulating valve (HV201) is provided on the low-pressure raw gas pipeline (2).

3. The separation method of a pressure swing adsorption gas separation system according to claim 1 or 2, characterized in that: The adsorption steps in the separation process include two adsorption steps: a high-pressure main adsorption step and a low-pressure auxiliary adsorption step. Moreover, when the high-pressure raw gas enters the adsorption tower, it corresponds to the high-pressure main adsorption step, and when the low-pressure raw gas enters the adsorption tower, it corresponds to the low-pressure auxiliary adsorption step.

4. The separation method according to claim 3, characterized in that Each adsorption tower undergoes the following steps in a cyclic sequence: High-pressure main adsorption step: high-pressure feed gas enters the adsorption tower from the inlet end, strong adsorbates are adsorbed, and weak adsorbates flow out of the adsorption tower; Multiple pressure reduction steps: the gas in the adsorption tower flows out of the adsorption tower from one or both of the outlet and inlet ends of the adsorption tower, and the pressure in the adsorption tower is reduced; Regeneration step: The strong adsorbate in the adsorption tower is desorbed from the adsorbent and leaves the adsorption tower, and the adsorbent is regenerated; Multiple pressurization steps: using gas from other adsorption towers to pressurize the adsorption tower; Low-pressure auxiliary adsorption step: low-pressure feed gas enters the adsorption tower from the inlet end, strong adsorbents are adsorbed, and weak adsorbents increase the pressure in the adsorption tower; Final pressure-raising step: The step in which the pressure in the adsorption tower is raised to the pressure of the high-pressure main adsorption step.

5. The separation method according to claim 4, characterized in that The depressurization step provides pressurized gas to the adsorption tower in the pressurization step or provides flushing gas to the adsorption tower in the flushing and regeneration step or directly discharges the adsorption tower as waste gas.

6. The separation method according to claim 4, characterized in that In the regeneration step, the regeneration method is one of flushing regeneration and vacuum regeneration, or a combination of the two methods.

7. The separation method according to claim 4, characterized in that The low-pressure auxiliary adsorption step is carried out simultaneously with the pressure-raising step or separately.

8. The separation method according to claim 7, characterized in that During the pressurization step, the gas from other adsorption towers enters the adsorption tower from one or both of the outlet and inlet ends of the adsorption tower.

9. The separation method according to claim 7, characterized in that The low-pressure feed gas is one or more streams, and accordingly, the low-pressure auxiliary adsorption step is one or more.

10. The separation method according to claim 4, characterized in that The pressurized gas in the final pressurization step comes from one or two combined gases of the weakly adsorbed material at the outlet of the adsorption tower in the high-pressure main adsorption step and the high-pressure feed gas.

11. The separation method according to claim 4, characterized in that The high-pressure raw gas and the low-pressure raw gas are the same gas, and the low-pressure raw gas is a gas obtained by reducing the pressure of a portion of the high-pressure raw gas.

12. The separation method according to claim 4, characterized in that The high-pressure raw gas and the low-pressure raw gas are two gases with different pressures and compositions.

Images